Light emitting diode light structures

ABSTRACT

A Light Emitting Diode (LED) light includes a bridge rectifier configured to be powered by an alternating current power source and to produce a rectified output. Control circuitry couples to the bridge rectifier and is configured to produce a shunt signal when the rectified output is less than a threshold voltage. A series connected Light Emitting Diode (LED) string includes a first group of LEDs and a second group of LEDs. A switch couples to a first side of the second group of LEDs and is controlled by the shunt signal to deactivate the second group of LEDs. The control circuitry may include a ratio metric series resistor string configured to sense a proportion of the rectified output and an inverter configured to generate the shunt signal based on the proportion of the rectified output.

CROSS-REFERENCE TO PRIORITY APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application Ser. No. 61/748,306 filed Jan. 2, 2013, which isincorporated herein by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to Light Emitting Diode (LED) lighting,and more particularly to circuitry for driving LED lighting and LEDlighting containing such circuitry.

2. Description of the Related Art

Electrical lighting is widely used all around the world, and has beenfor close to a century. For most of this time, the dominant form ofelectrical lighting has been incandescent light bulbs. However otherforms of light bulbs are becoming more popular in recent years.

Incandescent light bulbs pass an electrical current through a wire(called the filament) which causes the wire to heat up until it becomeswhite hot and emits light. Incandescent light bulbs are cheap, reliable,and very widely used, however most of the energy that they consume isemitted as waste heat rather than as useful light. Mainly because ofthis waste heat, the majority of the energy consumed by an incandescentlight bulb is wasted, and the efficiency of incandescent light bulbs istypically as low as 2%-3%.

Compact fluorescent light bulbs (also known as CFL bulbs) use afluorescent tube which is folded to fit in the space of an incandescentlight bulb, allowing the use of a CFL light bulb in place of anincandescent light bulb. The fluorescent tube generates light throughgas discharge by using electricity to excite a mercury vapor, which thenemits ultraviolet light, which in turn is converted to visible light bya phosphor that coats the inside of the tube. CFL light bulbs aresignificantly more efficient than incandescent light bulbs, with typicalefficiencies of 10% or so.

Unfortunately, CFL light bulbs are more complicated to manufacture thanincandescent light bulbs, as they require a ballast to limit the currentin the fluorescent tube after startup. Also, dimmer switches arecommonly used with light bulbs, and CFL light bulbs are not verycompatible with dimmer switches. Complications such as these make themanufacture of CFL light bulbs more expensive than incandescentbulbs—typically a CFL light bulb will cost several times more than anincandescent light bulb with the same level of light output. Finally,CFL light bulbs contain small amounts of mercury which is hazardous tohumans and which makes it more difficult to dispose of them safely.

Light Emitting Diode light bulbs (also known as LED light bulbs) areeven better than CFL light bulbs. The LEDs used in LED light bulbs arerapidly increasing in efficiency and light output, which allows LEDlight bulbs to get better over time. At typical efficiencies of 15% orso, LED light bulbs already offer higher efficiencies than CFL bulbs,and this efficiency advantage is expected to increase over time. Also,LED light bulbs do not contain hazardous materials, and are moreflexible than CFL light bulbs. For example LED light bulbs typicallywork better with dimmer switches which are commonly used by consumers.

Unfortunately, LED light bulbs are currently more expensive than CFLbulbs, and they are significantly more expensive than incandescentbulbs. Even with today's prices, the energy savings over a multi-yearperiod of use is sufficient to justify the extra cost of LED lightbulbs. This is especially true given that LED light bulbs typically havea longer lifetime than CFL bulbs, and a significantly longer lifetimethan incandescent bulbs. The prices of LED bulbs are expected to declinein the future. As these prices decline, any remaining consumerresistance to using LED bulbs will reduce, and LED light bulbs areexpected to become the dominant type of light bulb.

LED light bulbs use light emitting diodes (commonly referred to as LEDs)to generate light. LEDs operate by running electrical current through aforward biased diode junction which then emits monochromatic photons oflight. These monochromatic photons are then converted to broad spectrumwhite light by use of a phosphor. The LEDs typically need to be suppliedwith a voltage in the region of 3.5V or so. In order to maximize thelight output from the LED, and minimize flicker in the resulting lightoutput, it is normal to drive the LED with a constant direct current(DC). It is also possible to use multiple colors of LEDs (typically red,green, and blue LEDs) to generate a broad spectrum of light without theuse of a phosphor, although this is not common.

The light emitted by an LED is much more strongly correlated with thecurrent flowing through the LED than with the voltage dropped across theLED. In order to more closely match the light output from multiple LEDs,it is more effective to match the current provided to each LED than tomatch the voltage provided to each LED. Therefore, it is preferred toconnect several LEDs into a series configuration (an LED “string” asshown in item 110 in FIG. 1) than to connect several LEDs in parallel(as shown in item 120 in FIG. 1). An additional benefit of connectingLEDs in series is that the driving voltage is higher (N×˜3.5V, where Nis the number of LEDs in series), and the total driving currents arelower, thereby allowing for a more efficient design for the drivingcircuit.

The power supply for an LED light bulb is typically an alternatingcurrent (AC) voltage from a power mains supply. In various parts of theworld this supply will be a sine wave with a voltage of 120V RMS (whichis equal to 170V peak, or 340V peak-to-peak) or 240V RMS (which is equalto 340V peak, or 680V peak-to-peak), and a frequency of approximately 50Hz or 60 Hz. The LED light bulb takes energy from this AC supply, andconverts it to a form that is suitable for the LEDs to consume.

Additionally, the LED light bulb will need to have a power factor (PF)of close to 1.0, which means that the current taken from the mainssupply should be in direct proportion to the voltage of that supply.Expressed another way, this means that the LED light bulb should presenta purely resistive load to the mains supply.

This requirement significantly complicates the design of an LED lightbulb. If an LED light bulb has a PF of 1.0, then the energy taken fromthe mains supply will mostly be concentrated into short periods alignedwith the peaks of the voltage from the mains supply (item 210 in FIG.2), but the energy consumed by the LEDs will ideally be at a constantlevel (item 220 in FIG. 2). Achieving this requires energy storage forshort periods of time inside the LED light bulb.

One other important metric of the performance of light bulbs is flicker,which is the variation in the light output from the light bulb overshort periods of time. The human visual system is not especiallysensitive to flicker above about 20 Hz, as evidenced by the fact thatvideo displays often display video content with a 24 Hz frame rate, atwhich point most people cannot visually detect that the display isflickering, although displays often operate at multiples of thisfrequency in order to make flickering even less apparent. At lowerfrequencies however, say 10-15 Hz, flicker becomes very detectable (andannoying) for the human visual system, and has been known to causehealth effects in some cases.

Incandescent light bulbs do not demonstrate significant flicker. Theenergy supplied to the light bulb by an AC supply occurs primarilyconcentrated in short bursts corresponding to the peaks of the ACvoltage, however the filament retains heat for a long enough period thatit smoothens out these peaks to generate light at an almost constantlevel.

CFL light bulbs also do well with flicker management, because thephosphor demonstrates something called phosphor persistence, where themonochromatic photons of light absorbed by the phosphor are emitted asbroad spectrum light after a random delay, leading to a smoothing effecton the level of light output and reducing flicker. Since LED lights usea similar approach with a phosphor converting a monochromatic photonsource into broad spectrum light, their phosphor has a similar flickersmoothing effect.

A challenge with LED light bulbs today is heat dissipation. Incandescentlight bulbs emit a large percentage of the energy they consume as wasteheat, however most of the waste heat is emitted as infra-red light, andthey do not contain any especially heat sensitive components, so they donot require specialized heat handling features. Per unit of useful lightemitted, LED light bulbs waste less energy as heat; however most of thisheat is not radiated and needs to be conducted away from the LEDs usinga heat sink. Because of this, LED light bulbs are typically dominated bytheir heat sinks, and this contributes a significant proportion of themanufacturing cost of a current LED light bulb.

The performance of LEDs is getting better, and the amount of light thatthey output per unit of energy consumed is going up. Current lab designsof LEDs emit as much as 2 x more lumens of light per watt than the LEDstypically used in current production LED light bulbs. When these LEDsare used in production products, their 2× higher light output will meanthat they generate less waste heat per LED, but more importantly, theirhigher light output will mean that only half as many LEDs are requiredfor the same level of light output. Thus, a 2 x improvement in lightoutput per watt consumed will result in an approximately 3× decrease inwaste heat per LED light bulb.

Improvements in this area will have a large impact in the heatdissipation required in LED light bulbs. As the efficiency of the LEDsthemselves continues to improve, this heat dissipation problem willbecome much less severe, and the need for extensive heat handling willbecome much less significant.

The other remaining problem with current LED light bulbs is that theyrequire power conversion electronics to convert the power supplied bythe mains connection to a form that can be used by the LEDs themselves.The LED electronics also are responsible for managing other functions,such as managing the power conversion electronics to keep the powerfactor as high as possible, adjusting the light output of the LEDs basedon the operation of a dimmer switch, adjusting the light output of theLEDs to account for aging and temperature effects, and other functions.The LED electronics add cost and size to LED light bulbs. They alsocontribute to waste heat when the power conversion electronics don'tconvert energy with perfect efficiency.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates prior art LED strings and LED arrangements;

FIG. 2 is a graph illustrating an alternating current cycle along withLED power needs graphed therewith;

FIG. 3 illustrates an LED string having a plurality of series connectedLEDs;

FIG. 4 illustrates an LED light driven by a full-wave rectified voltagealong with graphs illustrating voltages driving the LED light;

FIG. 5 illustrates voltage, current, and lumens graphs corresponding tothe LED light of FIG. 4;

FIG. 6 illustrates an LED light contrasted according to one or moreembodiments of the present invention;

FIG. 7A illustrates an LED light constructed according to anotherembodiment of the present invention;

FIG. 7B illustrates an LED light constructed according to anotherembodiment of the present invention with dimmer control;

FIG. 7C illustrates an LED light constructed according to anotherembodiment of the present invention with voltage sensing circuitry anddimmer control;

FIG. 7D illustrates an LED light constructed according to anotherembodiment of the present invention with current sensing circuitry;

FIG. 7E illustrates an LED light constructed according to anotherembodiment of the present invention with current sensing circuitry andmultiple tap impedance adjust circuitry;

FIG. 7F illustrates behavior of an LED light constructed according tothe present invention as compared to an LED light without linearization;

FIG. 7G illustrates an LED light constructed according to anotherembodiment of the present invention with current sensing circuitry andmultiple tap impedance adjust circuitry using bipolar transistors;

FIG. 8 illustrates an LED light constructed according to anotherembodiment of the present invention embodied in a conventional lightbulb form;

FIG. 9 illustrates an LED light constructed according to an embodimentof the present invention having electronics located in module remote tomultiple LED bulbs;

FIG. 10 illustrates an LED light constructed according to anotherembodiment of the present invention having electronics located in moduleremote to multiple LED bulbs;

FIG. 11 illustrates an LED light constructed according to still anotherembodiment of the present invention having electronics located in moduleremote to multiple LED bulbs;

FIG. 12 illustrates an LED light constructed according to anotherembodiment of the present invention embodied in a conventional lightbulb form with electronics located in a base;

FIG. 13A illustrates an LED light constructed according to an embodimentof the present invention having electronics located in module remote tomultiple LED bulbs and having kick start circuitry;

FIG. 13B illustrates an LED light constructed according to an embodimentof the present invention having electronics located in module remote tomultiple LED bulbs and having kick start circuitry respective to eachLED bulb;

FIG. 14 illustrates an LED light constructed according to an embodimentof the present invention having kick start circuitry shown in detail;

FIG. 15 illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to relay controlinformation to the LED electronics;

FIG. 16 illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to wirelessly relaycontrol information to the LED electronics;

FIG. 16A illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to relay controlinformation to the LED electronics and to service wirelesscommunications with a client device;

FIG. 16B illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to wirelessly relaycontrol information to the LED electronics and to service wirelesscommunications with a client device;

FIG. 16C illustrates LED light constructed according to anotherembodiment of the present invention having LED electronics respective tomultiple LED bulbs and a wall mounted switch configured to wirelesslyrelay control information to the LED electronics and to service wirelesscommunications with a client device;

FIG. 16D illustrates three differing embodiments of an LED lightcontroller constructed according the present invention that supportscommunications with remote devices;

FIG. 16E illustrates an embodiment of an LED light controllerconstructed according the present invention that supports communicationswith remote devices;

FIG. 16F illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured control the LED lightpaired therewith;

FIG. 16F1 illustrates a ceiling mounted LED light constructed accordingto an embodiment of the present invention with a remote control;

FIG. 16F2 illustrates an LED light constructed according to anembodiment of the present invention with a remote control;

FIG. 16F3 illustrates an LED light constructed according to anotherembodiment of the present invention with a remote control;

FIG. 16G illustrates an LED light constructed according to an embodimentof the present invention with multiple wave rectification circuits;

FIG. 16H illustrates an LED light constructed according to anotherembodiment of the present invention with multiple wave rectificationcircuits coupled via transformer;

FIG. 16I illustrates an LED light constructed according to an embodimentof the present invention having a high voltage protection circuit;

FIG. 16J illustrates an LED light constructed according to an embodimentof the present invention having a surge protection circuit;

FIG. 16K illustrates an LED light constructed according to an embodimentof the present invention having LED bulbs accessible via jumper;

FIG. 16L illustrates an LED light constructed according to an embodimentof the present invention having differing LED bulb connection options;

FIG. 17 illustrates an LED light string constructed according to anembodiment of the present invention in a multiple layer semi conductivesubstrate;

FIG. 17A illustrates an LED light string constructed according toanother embodiment of the present invention in a multiple layer semiconductive substrate;

FIG. 18 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate;

FIG. 19 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate;

FIG. 20 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate;

FIG. 21 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate; and

FIG. 22 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate.

DETAILED DESCRIPTION

According to one or more aspects of the present invention, an LED lightbulb includes improved power conversion electronics. The powerconversion electronics service an LED string 310 as illustrated in FIG.3 and its operation depends on the AC peak voltage, and includes enoughLEDs so that all the LEDs are fully turned on and outputting light attheir peak value when the AC input voltage is at its peak value. Forexample, with LEDs with a peak supply voltage of 3.6V, and a 120Vrms ACsupply (=120*2^(0.5)=169V peak), we will need 47 LEDs in the string.

FIG. 4 illustrates an LED light driven by a full-wave rectified voltagealong with graphs illustrating voltages driving the LED light. An LEDlight 410 built using a LED string is shown in FIG. 4, and the expectedperformance of such a light bulb is shown in FIG. 5. The AC voltagesupply is shown at graph 412 of FIG. 4 and the rectified AC voltage isshown at 414 of FIG. 4. The AC voltage (Vmains), AC current (Imains),and lumens produced by the LED light bulb 410 are illustrated in FIG. 5.

Since there is a very non-linear relationship between the voltage acrossa LED and the light output, the light output from the LEDs will varythroughout the full cycle of the AC input voltage as show in FIG. 5.This leads to a flicker in the light output that happens at twice thefrequency of the input AC supply (i.e. 100 Hz in areas with 50 Hz mainssupply, 120 Hz in areas with 60 Hz mains supply), although the actuallight output from the LED light bulb will be smoothed out quite a bit bythe phosphor persistence of the phosphors used to convert themonochromatic photons from the LEDs to broad spectrum light from the LEDlight bulb.

There are two other major disadvantages to a LED string. First, the LEDswill be inactive for a significant proportion of the AC cycle, whichmeans that the LEDs will operate with a large peak power to averagepower ratio. A higher peak to average power ratio may increase thecumulative power rating of all of the LEDs needed in an LED light bulbto achieve a certain level of light output. Second, the shape of thecurrent waveform consumed by the LEDs will be quite far away from theideal of a sine wave that is in phase with the AC voltage sine wave.This will lead to a sub-optimal power factor for an LED light bulb madewith a LED string.

FIG. 6 illustrates an LED light contrasted according to one or moreembodiments of the present invention. It is possible to improve upon theperformance of a LED string significantly with a circuit as shown inFIG. 6. The LED light 610 of FIG. 6 includes an AC power source 612, abridge rectifier 614, a control circuitry 616, a switch 617, and aseries connected LED string 618. The series connected LED string 618includes a first group of LEDs including LED 620 and above and a secondgroup of LEDs including LED 630 and below. The control circuitry 616includes a ratio metric series resistor string and an inverter that, inoperation, turn on the switch 617 when the voltage produced by thebridge rectifier 614 is below a threshold voltage and to turn off theswitch 617 when the voltage produced by the bridge rectifier 614 isabove the threshold voltage.

The bridge rectifier 614 is configured to be powered by an alternatingcurrent power source (AC power source 612) and to produce a rectifiedoutput. The control circuitry 616 couples to the bridge rectifier and isconfigured to produce a shunt signal when the rectified output is lessthan a threshold voltage. The series connected Light Emitting Diode(LED) string 630 includes a first group of LEDs (620 and above) and asecond group of LEDs (630 and below). The switch 617 couples across thesecond group of LEDs and controlled by the shunt signal to deactivatethe second group of LEDs.

In one embodiment, a number of the first group of LEDs is approximatelyequal to a number of the second group of LEDs. In another embodiment, anumber of the first group of LEDs is greater than a number of the secondgroup of LEDs. The first group of LEDs may include one or more than oneLED. The second group of LEDs may include one or more than one LED.

The control circuitry 616 may include a ratio metric series resistorstring configured to sense a proportion of the rectified output and aninverter configured to generate the shunt signal based on the proportionof the rectified output. The inverter may include a transistorconfigured to receive the proportion of the rectified output and aresistor coupled to the transistor and configured to generate the shuntsignal based on the proportion of the rectified output.

The switch 617 may be a field effect transistor having gate configuredto receive the shunt signal and a drain and source connected in shuntacross the second group of LEDs. In another embodiment, the switch 617may be a bipolar transistor having a base configured to receive theshunt signal and an emitter and collector connected in shunt across thesecond group of LEDs.

The control circuitry and switch are configured to effectively adjustthe length of the LED string to short out every LED from device 630 andbelow in the LED string 618, during the part of the AC cycle when thesupply voltage is less than the threshold voltage (which is equal to aportion of the peak voltage, e.g., 100%, 90%, 80%, 70%, 60%, etc.). Thiswill allow the remaining LEDs in the LED string 618 to see highervoltages than they would otherwise see during this part of the AC cycle(with switching device 617 closed/transistor turned on), leading tohigher levels of current and larger amounts of light output from theseLEDs than would otherwise be the case without the LED string shorteningcircuit.

Teachings of the present invention address disadvantages of the LEDstring mentioned previously, among other disadvantages. Accordingly, theoverall light output goes up, thereby improving the average to peaklight output ratio. And two, the current waveform now allows greateramounts of current at periods where the LED string was previously notconducting current, improving the power factor.

For example, in one simulation, a LED string with 47 LEDs has a peak toaverage LED power ratio of 4.04 to 1, and a power factor of 81.58%.Because of the simplicity of the LED electronics, there is very littleenergy lost in power conversion, and 99.2% of all of the energy used bythe LED light bulb will be consumed by the LEDs. It is true that asignificant portion of the energy consumed by the LEDs will be wasted asheat, however this constraint is common to all possible designs of anLED light bulb.

The modified LED string circuit shown in FIG. 6 manages to improve onthis performance significantly. If device 610 is configured to remove 8LEDs from the string whenever the input voltage is below 145V, the peakto average LED power ratio improves to 3.30 to 1, and the power factorimproves to 87.91%. The energy efficiency of this design continues toremain excellent, with 99.1% of the energy consumed by the LED lightbulb being delivered to the LEDs.

FIG. 7A illustrates an LED light constructed according to anotherembodiment of the present invention. It is possible to further improveupon the LED string design by adding additional tap points to allow morevariation in the number of LEDs active in the LED string. FIG. 7 showsone such circuit 710. The device 710 of FIG. 7A includes a bridgerectifier 714 configured to be powered by an alternating current powersource 712 and to produce a rectified output. The device 710 furtherincludes control circuitry 716 coupled to the bridge rectifier 714, thecontrol circuitry 716 configured to produce a first shunt signal toswitch 718 based upon the rectified output and at least one firstvoltage threshold and to produce a second shunt signal to switch 720based upon the rectified output and at least one second voltagethreshold. A series connected Light Emitting Diode (LED) string 722includes a first group of LEDs 724, a second group of LEDs 726, and athird group of LEDs 728. The first switch 718 couples to a first side ofthe second group of LEDs 726 and is controlled by the first shunt signalto deactivate the second group of LEDs 726. The second switch 720couples to a first side of the third group of LEDs 728 and is controlledby the second shunt signal to deactivate the third group of LEDs 728.

If the circuit 710 in FIG. 7A is configured to remove 4 LEDs from theLED string when the voltage from the diode bridge is below 155V, andremove a further 4 when the voltage is below 140V, then the peak toaverage LED power ratio improves yet again to 3.01 to 1, and the powerfactor improves to 89.58%.

In alternate embodiment of FIG. 7A, switch 718, instead of shunting toground, shuts across the second group of LEDs 726, such that when theswitch is closed (transistor is turned on), the second group of LEDs 726are disabled.

With one embodiment of the device 710 of FIG. 7A, a number of the secondgroup of LEDs 726 is approximately equal to a number of the third groupof LEDs 728. With another embodiment of the device of FIG. 7A, a numberof the first group of LEDs is greater than a number of the second groupof LEDs. The first group of LEDs may include one or more than one LED.The second group of LEDs may include one or more than one LED. The thirdgroup of LEDs may include one or more than one LED.

With the device 710 of FIG. 7A, the control circuitry may include aratio metric series resistor string configured to sense a firstproportion and a second proportion of the rectified output, a firstinverter configured to generate the first shunt signal based on thefirst proportion of the rectified output, and a second inverterconfigured to generate the second shunt signal based on the secondproportion of the rectified output. With this embodiment, the firstinverter may include a first transistor configured to receive the firstproportion of the rectified output and a first resistor coupled to thetransistor and configured to generate the first shunt signal based onthe first proportion of the rectified output and the second inverter mayinclude a second transistor configured to receive the second proportionof the rectified output and a second resistor coupled to the secondtransistor and configured to generate the second shunt signal based onthe second proportion of the rectified output.

The first or second switch may be a field effect transistor having agate configured to receive a respective first shunt signal with a drainand source connected in shunt across a respective group of LEDs. Inanother embodiment, the first or second switch may be a bipolartransistor having a base configured to receive a respective first shuntsignal and an emitter and collector connected in shunt across arespective group of LEDs.

It is possible to include multiple additional tap points at variouspoints in the LED string, and triggered at various AC input voltagepoints, allowing for additional incremental improvements in the peak toaverage LED power ratio, and in the PF. Inverters created by R4 and R5and the FETs attached below them could be replaced by any type ofinverter including, but not limited to, full CMOS inverters, PMOSinverters, NPN or PNP inverters.

FIG. 7B illustrates an LED light constructed according to anotherembodiment of the present invention with dimmer control. A modificationallows dimmer control of the further improved LED string. Gating Dim 1and Dim 2 to a logic-high allows the further improved LED string tooperate as the circuit in FIG. 7A. However, gating dimmer control signalDim 2 to a logic-low while keeping Dim 1 at a logic-high prevents deviceM6 from ever turning off. This action switches fewer diodes across therectified supply causes an increase in light output, thereby offeringtwo levels of dimmer capability. Furthermore, by switching Dim 1 and Dim2 to various logic levels as shown in Table 1 below, allows three dimmerlevels to be achieved.

One drawback is that the PF of the LED light bulb will vary with Dim 1and 2 settings as shown in the Table 1. In fact, the PF is worse whenthe LED string is consuming the most power. This will be unacceptable insome applications.

TABLE 1 Brightness and PF for Dim states Logic State Dim 1 0 0 1 1 Dim 20 1 0 1 Brightness high high medium low Approximate 0.7 0.7 0.8 0.9 PF

FIG. 7C illustrates an LED light constructed according to anotherembodiment of the present invention with voltage sensing circuitry anddimmer control. Other switching schemes could be used to achieve a highPF at high brightness. When Dim 1 and Dim 2 are set to a logic-high, thecircuit behaves exactly like the circuit in FIG. 7A with a high PF ofabout 0.9. However, when Dim 1 is set to a logic-low and Dim 2 ismaintained at a logic-high, the LED string brightness is reduced alongwith the PF, but a reduced PF is not as big of an issue when the LEDstring in drawing less power from the supply. Likewise, when both Dim 1and 2 are set to a logic-low, the PF again is reduced, but so are thebrightness and the power drawn from the supply. See Table 2.

TABLE 2 Brightness and PF for each Dim state Logic State Dim 1 0 0 1 1Dim 2 0 1 0 1 Brightness low medium high high Approximate low mediumhigh (0.9) high (0.9) PF

There are other possible switching schemes that will yield varyingperformance of brightness and PF. Circuits constructed according to thepresent invention use various switching schemes to achieve improved PF,dimmer capability or both in one switching circuit. Any electronictechnology could be used to accomplish the switching discussedincluding, but not limited to, bipolar, MOSFET, GAS, MEMS, integratedcircuit, or discrete component technologies.

FIG. 7D illustrates an LED light constructed according to anotherembodiment of the present invention with current sensing circuitry. Toimprove PF, the non-linear nature of the LED string can be improvedusing a current sensing circuit as shown in FIG. 7D. The current in thediode string (Id) is sensed by the current sense circuit. The currentsense circuit may be a resistor. Id is then compared to a referencecurrent (Ir) generated by the reference current circuit. The referencecurrent circuit may be comprised of two resistors. The currentdifference is used to adjust the impedance of the diode string such thatit appears more linear or resistive and less non-linear like a diode.The impedance adjust circuit may be implemented with a switch.

A low voltage (Vr) on the LED string, will produce an Id=0 amps, becausethe LED's have insufficient voltage to forward bias them. Ir, however,will not be zero which, when compared to Id will activate the impedanceadjust circuit to shunt one tap of the diode string to bottom of the LEDstring. Id initially will be zero, but eventually, at some Vr level, Idwill exceed Ir and cause the impedance adjust circuit to free the tapthat was shunted to the bottom of the LED string. This “freeing the tap”can happen continuously or all at once with a switch. This freeing ofthe tap will increase the impedance of the LED string removing some ofits non-linearity.

FIG. 7E illustrates an LED light constructed according to anotherembodiment of the present invention with current sensing circuitry andmultiple tap impedance adjust circuitry. With FIG. 7E, an LEDlinearization scheme uses current sensing and multiple taps. It operatesmuch like the scheme in FIG. 7D, but uses multiple taps to adjust theimpedance of the LED string. The multiple taps are better suited for adigital or switched implementation rather than a continuous or analogimplementation. As Ir increases and Id varies based on switch positionof the taps, the impedance adjust circuit tries to maintain Id=Ir,creating a more linearized LED string.

FIG. 7F illustrates behavior of an LED light constructed according tothe present invention as compared to an LED light without linearization.FIG. 7F compares the I-V curves of a diode string and a resistor (top)and a linearized diode string and a resistor (bottom). Initially, whenthe voltage Vr is zero, all of the impedance adjust circuit switches areshorting LED string taps to the bottom of the LED string. As Vrincreases, the difference between Ir and Id causes the impedance adjustcircuit to releases the taps of the LED string from the bottom of theLED string in a sequential manner starting from the top tap. This causesthe current in the LED string to decrease at each step of this process.That is the cause of the discontinuities in the LED string I-V curve inFIG. 7F.

FIG. 7G illustrates an LED light constructed according to anotherembodiment of the present invention with current sensing circuitry andmultiple tap impedance adjust circuitry using bipolar transistors. Theexpanded view of the LED linearization circuit uses multiple taps andcurrent sense. An approximate current Ir is setup in resistor R thatflow through the NPN current mirror into the impedance adjust circuit.The current mirror has a mirror ratio of 1:n where n can have any valueincluding 1. Another current mirror is used to send a proportion of theLED string current to the impedance adjust circuit. This current mirrorhas a mirror ratio of 1:n where n can have any value including 1. Theimpedance adjust circuit compares the mirrored currents and sequentiallyadjusts the taps that are switched to the bottom of the LED string.

FIG. 8 illustrates an LED light constructed according to anotherembodiment of the present invention embodied in a conventional lightbulb form. With FIG. 8, an LED light bulb includes electronics. The bulboperates within a standard 120V or 240V AC light fixture. LEDelectronics in the base of the bulb includes a power conversion circuitto convert the AC supply power to a form suitable for the LEDs. The LEDsused normally require a phosphor, which can either be coated on a globesurrounding the LEDs and circuit boards, or alternately, the LEDsthemselves can include the phosphor.

It is possible to move the LED electronics located in the LED light bulbto a light switch, which allows multiple LED light bulbs to share theLED electronics. The LED electronics in an LED light bulb account for asignificant proportion of its complexity and cost of manufacturing saidLED light bulb, so moving this functionality to the light switch andpossibly sharing it between several LED light bulbs could reduce costs.

FIG. 9 illustrates an LED light constructed according to an embodimentof the present invention having electronics located in module remote tomultiple LED bulbs. In the embodiment of FIG. 9, the LED electronics inthe light switch would remain powered down until the switch is turnedon. When the switch is turned on, the LED electronics in the lightswitch power up and then begins to provide power to the LED light bulbs.

FIG. 10 illustrates an LED light constructed according to anotherembodiment of the present invention having electronics located in moduleremote to multiple LED bulbs. In FIG. 10, the LED electronics could beconnected to the AC mains supply all the time, and connected to the LEDlight bulbs via a switch. This would allow for a near zero startup timeas the output stage of the power conversion circuit would already beramped up to the necessary supply voltage at the time that the switchwas closed.

FIG. 11 illustrates an LED light constructed according to still anotherembodiment of the present invention having electronics located in moduleremote to multiple LED bulbs. In the embodiment shown in FIG. 11, thepower conversion circuit is permanently connected to both the AC mainssupply and the LED light bulbs. The operation of the power conversioncircuit would then be controlled by a different means, such as a button,switch, touch sensor, remote control, or other mechanism.

FIG. 12 illustrates an LED light constructed according to anotherembodiment of the present invention embodied in a conventional lightbulb form with electronics located in a base. It is be possible to useone of these LED light bulbs that did not include LED electronics in astandard light socket through the use of an adapter as shown in FIG. 12.The adapter would contain the LED electronics needed to supply the LEDs,by converting power from the AC mains supply provided by the standardlight bulb socket.

No matter if the LED electronics are located in the light switch or inthe base of the LED light bulb, this LED electronics may need some timeto power up fully and begin supplying power to the LEDs in the LED lightbulb. For some LED light bulbs in the market today, this “turn-on” delaycan be long enough to be noticeable by the consumer. A long “turn-on”delay is not desirable, so it would be beneficial to reduce or eliminateit.

FIG. 13A illustrates an LED light constructed according to an embodimentof the present invention having electronics located in module remote tomultiple LED bulbs and having kick start circuitry. It is possible toshorten the “turn-on” delay through the use of a “kick start” circuit asshown in FIG. 13A, which bypasses the normal power conversionelectronics and which operates for only a short period of timeimmediately after the LED light bulb is turned on.

FIG. 13B illustrates an LED light constructed according to an embodimentof the present invention having electronics located in module remote tomultiple LED bulbs and having kick start circuitry respective to eachLED bulb. An alternative embodiment of the kick start circuitapplication is shown in FIG. 13B. In this embodiment of the presentinvention, the kick start circuit is embedded in each individual lightbulb. In this way, an ordinary wall light switch can be used.

The efficiency of the power conversion performed by the LED electronicsis an important metric, since this will partially determine theefficiency of the LED light bulb, but because the kick start circuitonly operates for a short period of time when the LED light bulb isturned on, its efficiency is much less important.

FIG. 14 illustrates an LED light constructed according to an embodimentof the present invention having kick start circuitry shown in detail.Initially, when power is applied to the LED current regulator,high-valued resistor R1 impresses 54V on the zener diode. The n-channeltransistor, connected in a source follower configuration, driveslow-valued resistor R2 and diode D2 to about 51V. This forward biases D2and immediately powers the LED string with about 50V creatinginstantaneous light. Some delay later, when the LED current regulatorcircuit powers up, D1 forward biases, establishing about 57V on the LEDstring. With 57V impressed on the LED string, D2 becomes reversed biasedand current no longer flows through D2. This disables the kick startcircuit allowing the LED current regulator to power the LED string.

FIG. 15 illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to relay controlinformation to the LED electronics. LED light bulbs normally include LEDelectronics to convert power from the AC mains supply to a form suitablefor use by the LEDs. It is usually possible to also include someinexpensive control circuitry that implements features that can increasethe usefulness of the LED light bulbs, as shown in FIG. 15.

One such feature could be to transmit control information from the lightswitch to the LED light bulb over the power wire. The controlinformation could instruct the LED light to turn on or off, or couldcontrol dimming of the LED light's output, thereby allowing for theconfiguration of lights and switches in a house to be changed withouthaving to rewire the house. The control information could also be usedto control the operation of other devices, such as ceiling fans, airconditioning, and heater units, thereby allowing an intelligent switchto control multiple devices in a house.

There are a number of means for sending such control information overthe power wires. One means would be to send a signal modulated at afrequency well above the 50 or 60 Hz normally used by AC mains power.Other data transmission means could be used such as PPM, PDM, PWM, FM,AM QPSK, OFDM, etc. . . . .

FIG. 16 illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to wirelessly relaycontrol information to the LED electronics. The signal could betransmitted from the light switch to the LED lights by other means, suchas radio frequency, or infrared light as shown in FIGS. 16 and 16A. Thissignal could also contain data such as video, pictures, music, orInternet data.

FIG. 16A illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to relay controlinformation to the LED electronics and to service wirelesscommunications with a client device. Light from LEDs is commonly used totransmit data at very high data rates, such as in fiber opticcommunication, as well as at medium to low data rates, such as ininfrared remote controls. An intelligent LED light bulb could be used totransmit information to other devices such as laptops using LED light asshown in FIG. 16A. It would also be possible for data to be transmittedby a remote device and received by the LED light bulb.

In FIG. 16A, a video source digital output is sent to the wall switchmodule and converted to a power line data stream. This power line datastream is sent to the LED light bulbs where their LED electronicsmodulates this data stream into high frequency light pulses of low andhigh intensity. A device, such as a laptop or smart phone, receives thisdata through a built-in or peripheral light receiving communicationdevice. This light receiving communication device may be a camera thatis mounted on the face of the laptop or smart phone or it may be anaftermarket USB plug in light communication device.

It may be necessary for reverse communication from the laptop or smartphone to the light bulb. In this case, the light bulb would need tocontain light receiving devices such as photodiodes. The reversecommunication path may be used to send data back to the wall switch, forerror checking and correcting or to maintain the communication link. Thedata stream sent over the power line may also require a reversecommunication channel. Modulation for the light communication mayinclude but is not limited to PWM, PPM, PDM, or communication thatcomplies with IEEE 802.15.7. Since the modulation frequency of the lightsignal is much higher than the persistence of the human eye, the flickerproduced is imperceptible.

This type of light communication does not have to be limited to LEDlight bulb to laptop or smart phone. It could also be LED light bulb toLED light bulb. This would allow the light bulbs to act as repeaters orto synchronize or cooperate with each other such as in a mesh network.

FIG. 16B illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured to wirelessly relaycontrol information to the LED electronics and to service wirelesscommunications with a client device. The communication between thelaptop or smart phone does not need to be light communication, it mayalso be radio frequency communication, as shown in FIG. 16B. Someexamples of wireless communications that could be used are802.11a/b/g/n, WiMAX, 3G, 4G, or Bluetooth. This type of communicationcould leverage the wireless communications that are already built in tolaptops and smart phones. With wireless communication, the wall switchmodule could send the source data to the LED light bulbs through radiofrequency as shown in FIGS. 16B and 16C instead of over the power linesas depicted in FIG. 16A.

FIG. 16C illustrates LED light constructed according to anotherembodiment of the present invention having LED electronics respective tomultiple LED bulbs and a wall mounted switch configured to wirelesslyrelay control information to the LED electronics and to service wirelesscommunications with a client device. FIG. 16C depicts a similar systemto that in FIG. 16B, but with the wall switch module powered from abattery rather than the 120 VAC mains. In this way, the wall switchmodule can be mobile and embedded into a hand-held home automationcontroller or smart phone.

The communication of signals does not need to be only from a lightswitch to LED light bulbs, the signal could also go in the oppositedirection from the LED light bulb to the switch, or from one LED lightbulb to another LED light bulb.

One use of multi direction transmission of such a signal would be toimplement energy saving features. Some or all LED light bulbs could beequipped with a motion sensor, or a sound sensor, or a similar sensorthat would allow the LED light bulbs to sense when an occupant ispresent, and then turn off or dim the light if no occupancy is detectedfor a suitable period of time. Multiple LED light bulbs could cooperateso that a single LED light bulb detecting an occupant would besufficient to keep several LED light bulbs operating at full brightnessin the vicinity of the occupant.

FIG. 16D illustrates three differing embodiments of an LED lightcontroller constructed according the present invention that supportscommunications with remote devices. Three communication modules havebeen discussed; power line, light and radio frequency (RF). Blockdiagrams of each of these systems is shown in FIG. 16D. The RFcommunication system (a) contains a controller that accepts informationin the form of data from a switch and a source. The data from the switchmight contain on/off control information or strobe or dimmerinformation. The data from the source might contain cable or satelliteset top box video and audio information or a digital data stream from aDVD or CD player or it might even contain information from a PC orinternet streaming device such as an Apple TV or Roku entertainmentdevice.

The controller formats the data and provides Media Access Control (MAC)and physical layer (PHY) processing. These MAC and PHY functions mightinclude scrambling, coding, interleaving, mapping, FFT and IFFT, addingcyclic prefix, framing and error correction. The program module storesthe software and firmware code required by the controller. Memory is akey element of the program module.

After the data is formatted by the controller, it is passed to the RFcommunication module where is it converted to an analog signal, mixed ormodulated up to an RF frequency and transmitted by an RF power amplifierto an antenna. The antenna projects the RF signal through the air in apattern pre-determined by the physical shape and electrical propertiesof the antenna.

The light communication system (b) contains a controller that acceptsinformation in the form of data from a switch and a source. The datafrom the switch might contain on/off control information or strobe ordimmer information. The data from the source might contain cable orsatellite set top box video and audio information or a digital datastream from a DVD or CD player or it might even contain information froma PC or internet streaming device such as an Apple TV or Rokuentertainment device.

The controller formats the data and provides Media Access Control (MAC)and physical layer (PHY) processing. These MAC and PHY functions mayinclude scrambling, coding, interleaving, framing and error correction.The program module stores the software and firmware code required by thecontroller. Memory is a key element of the program module.

After the data is formatted by the controller, it is passed to the IR(infrared or light) communication module where is it converted to lightand transmitted through the air with a LED. The LED projects the lightthrough the air in a pattern pre-determined by the physical shape andelectrical properties of the LED.

The powerline communication system (b) contains a controller thataccepts information in the form of data from a switch and a source. Thedata from the switch might contain on/off control information or strobeor dimmer information. The data from the source might contain cable orsatellite set top box video and audio information or a digital datastream from a DVD or CD player or it might even contain information froma PC or internet streaming device such as an Apple TV or Rokuentertainment device.

The controller formats the data and provides Media Access Control (MAC)and physical layer (PHY) processing. These MAC and PHY functions mayinclude filtering, modulation, coding, carrier detection, framing,automatic gain control and error correction. The program module storesthe software and firmware code required by the controller. Memory is akey element of the program module.

After the data is formatted by the controller, it is passed to the powerline communication module where is it converted to an analog signal andtransmitted over the power line interface. The power line interfaceconditions and then couples the transmitted signal to the power linewhile rejecting the 120 VAC (or 240 VAC in other countries).

Communication means other than RF, light or power line could be used forcommunication between LED light bulbs and the wall switch controller.Each has its advantage and disadvantage.

FIG. 16E illustrates an embodiment of an LED light controllerconstructed according the present invention that supports communicationswith remote devices. The wall switch module connects to a power source(120 VAC mains, battery or conditioned supply), switch source,controller, program module, communication module and interface as shownif FIG. 16E. The interface provides impedance match and signalconditioning to the transmission media. The communication moduleprovides modulation, error correction and formatting of the data beforesending to the interface. The controller, by executing the programstored in the program module, provides functions such as MAC, encryptionand device pairing before sending the data from the switch and source tothe communication module. The power source provides power to all blocksin the system that requires power.

FIG. 16F illustrates an LED light constructed according to an embodimentof the present invention having LED electronics respective to multipleLED bulbs and a wall mounted switch configured control the LED lightpaired therewith. It is necessary to pair all devices in a lightingnetwork before control or communication can begin. To facilitate this, apairing function must be included in the wall switch module and each LEDelectronic device as shown in FIG. 16F. Pairing can be manual, like agarage door opener with remote, or automatic like a PC in a local areanetwork. Each of the LED electronics can be assigned an address or thewall switch module can assign a random address to each LED electronic.The wall switch module manages the pairing of the communication networkand the LED electronics serve the wall switch module pairing commands.In one preferred embodiment, pairing takes place the first time power isapplied to the wall switch module. From then on pairing is updated eachtime a new LED electronics is activated within the communication rangeof the wall switch module. If an LED electronic loses its pairing, thewall switch module will attempt to repair the lost device or the entirenetwork of LED electronics. Other pairing schemes are possible that willensure that all associated LED electronics are maintained in the networkat all times.

FIG. 16F1 illustrates a ceiling mounted LED light constructed accordingto an embodiment of the present invention with a remote control. FIG.16F2 illustrates an LED light constructed according to an embodiment ofthe present invention with a remote control. FIG. 16F3 illustrates anLED light constructed according to another embodiment of the presentinvention with a remote control. LED lighting, rechargeable batteriesand solar cells (photovoltaic cells) are becoming so efficient that anLED light bulb will operate 24 hours a day without being connected tothe power mains. FIGS. 16F1, 16F2, and 16F3 show systems that arecapable of this. During the day, the solar cells produce power fromambient light to operate the LED light bulb and to charge the battery.The control and charging electronics (CCE) manages this function. Duringthe night, the rechargeable battery will supply power for the light. Tocontrol the on/off state of the light, a remote control is used tomodulate the current produced by the solar cells. The CCE demodulateinformation sent from the remote and control the state of the LED lightbulb.

During the day, the solar cells produce a DC current Idc from theambient light and, when the remote control is activated, a modulatedcurrent Iac is created as shown in FIG. 16F2. The CCE charges thebattery from the Idc and demodulates Iac to determine the desired stateof the LED light bulb. Idc is used to power the light bulb. At night,Idc=0 amps requiring all power to come from the battery. Iac however,continues to determine the state of the LED light bulb.

In a wireless power system using an alternative embodiment of theinvention, constant light plus modulated light is sent from a remotedevice to create both Idc and Iac as shown in FIG. 16F3. In this way,power is derived without wires, from the remote control. This embodimentwill function at night and eliminates the need for a battery. Normally,the remote control would not be a handheld device, although it could be,but a device that is fixed in location, receiving power from a wire. Oneapplication might be decorative lighting, to prevent running wires up toa temporary overhead light. Another application might be a road signthat illuminates at night from the headlights of a car. Since remoteroad signs have no power source, the headlights of the car produce Idcand can be modulated to create Iac if control information is desired.

FIG. 16G illustrates an LED light constructed according to an embodimentof the present invention with multiple wave rectification circuits.Double bridge rectification can be used to reduce perceived flicker inthe system as shown in FIG. 16G. Though single bridge rectificationreduces the flicker by a factor of two by increasing the flicker ratefrom 60 Hz to 120 Hz, double bridge rectification reduces flicker byanother factor of two by increasing the flicker rate to 240 Hz. Inaddition, double bridge rectification significantly reduces the peak toaverage voltage seen by the LED string. An AC coupling circuit isrequired for this circuit to function properly. In this preferredembodiment, and RC filter for AC coupling is used.

FIG. 16H illustrates an LED light constructed according to anotherembodiment of the present invention with multiple wave rectificationcircuits coupled via transformer. A transformer can be used to AC couplethe two bridge rectifiers as shown in FIG. 16H. In this embodiment, thetransformer has a 1:n turns ratio where n=1. Any other turns ratio thatwould benefit the overall performance of the design could be used.Triple, quadruple and higher order bridge rectification are alsoconceivable for powering the LED string.

FIG. 16I illustrates an LED light constructed according to an embodimentof the present invention having a high voltage protection circuit. Surgeprotection or high voltage protection must be used to prevent the LEDstrings from being damaged in the event of lightning or perturbations inthe power supply. One such way to protect the LED string is to use ahigh voltage protection circuit as shown in FIG. 16I. If a high voltageevent passes through the bridge rectifier, it will be shunted to groundand dissipated as heat in the high voltage protection circuit. This willprotect the LED string, but not the bridge rectifier. The bridgerectifier is less sensitive to high voltage events than the LED string,so this type of high voltage protection will be suitable in manyapplications.

FIG. 16J illustrates an LED light constructed according to an embodimentof the present invention having a surge protection circuit. The highvoltage protection circuit or surge protection circuit can be addedbefore the rectifier as shown in FIG. 16J. With this placement of thesurge protector, both the rectifier and the LED string are protectedfrom unwanted and harmful high voltages and surges. In this placement ofthe surge protector, the surge protector must be more robust, because itmust deal with the higher voltages and more electrically hostileenvironment of the mains power supply. This is likely to increase thecost of the surge protection portion of the LED light bulb.

FIG. 16K illustrates an LED light constructed according to an embodimentof the present invention having LED bulbs accessible via jumper. Whenmanufacturing an LED light bulb based on the series LED string, jumperscan be used to tune the length of the LED string to make up for the maketolerance of the LEDs. One such design based on this technique is shownin FIG. 16K. In the factory, the maximum number of LEDs that will beused are installed in the LED light bulb. Humans or machines theninstall the appropriate number of jumpers to accommodate the maketolerance of the LEDs. This can be done while electrically testing theLED light bulb or through advance knowledge of the make tolerance of theLEDs that have been installed. In this way, the brightness of the LEDlight bulb can be tuned to the desired intensity level in the factory.

FIG. 16L illustrates an LED light constructed according to an embodimentof the present invention having differing LED bulb connection options.Another way to adjust the length of the LED string to correct formanufacturing tolerance of the LEDs is shown in FIG. 16L. This circuitallows the three LEDs at the bottom to be connected in series, parallel,or a series/parallel combination through the use of switches or jumpers.The three connection options that this preferred embodiment allows areshown to the left of the circuit diagram. Any number of jumpers could beused to connect any number of diodes in any series, parallel,series/parallel or LED shorting scheme to adjust the LED sting impedanceto correct for manufacturing tolerances of the LEDs.

Since some of the circuitry disclosed here make use of large numbers ofLED diodes arranged in an electrical string, it would also be useful todisclose circuitry applicable to the manufacturing of such LED strings.

Much current research is ongoing to determine how to output higherlevels of light from a single LED diode, and at higher levels ofefficiency. Improvements in this area can be combined with the circuitrydisclosed here, in order to create devices that combine higher levels oflight out and multiple LED diodes in a single device. If N multipleseries connected LED diodes were created in a single device, each LEDdevice could be 1/N times the size of the LED diode in a conventionalLED device, and output 1/N times as much light, but with N diodes inseries, the total light output would remain constant.

FIG. 17 illustrates an LED light string constructed according to anembodiment of the present invention in a multiple layer semi conductivesubstrate. One approach to doing this would be to manufacture multiplediodes on a single piece of silicon as shown in FIG. 17. Intrinsicsilicon does not conduct electricity very well, especially at lowertemperatures. An intrinsic silicon wafer or one that has been lightlydoped with p-type or n-type impurities could be implanted with heavydoses of P-type and N-type impurities from both sides as shown, in orderto make a series of LED diodes as shown in FIG. 17, which can then beconnected in series using conductors deposited on each side of thesilicon wafer. FIG. 17 shows the fabrication process and a cross sectionof such a device.

FIG. 17A illustrates an LED light string constructed according toanother embodiment of the present invention in a multiple layer semiconductive substrate. Implanting both sides of the wafer in undesirable,so an alternative fabrication technique could be used. FIG. 17A uses adeep implant for the bottom layer (n-type in this example) and a shallowimplant for the top layer (p-type in this example. This eliminates theneed to implant both sides of the wafer. The resulting series string ofdiodes in FIG. 17A is similar to that shown if FIG. 17.

FIG. 18 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate. An alternative manufacturing approach is shown inFIG. 18. Interconnects can be deposited on one side of the wafer asbefore, but the connections on the other side of the wafer could be madevia the substrate that the LED is mounted upon. If the resistance of theintrinsic silicon proves too high, or if it is preferred to manufacturethe LED diodes using an N-type or P-type wafer, then an alternatemanufacturing approach can be used as shown in FIG. 19.

FIG. 19 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate. In this case, a slice of silicon with a large areaP-N junction is manufactured and then attached to a substrate, then thewafer area between the desired LED diodes is removed using an etchingprocess, or a laser process, leaving free standing LED diodes attachedto a substrate. These LED diodes are then connected using wire bonds tocreate a series of LEDs connected in series on a single substrate. Analternate assembly process would be similar to FIG. 19, except thediodes would be cut into individual pieces before attaching to thesubstrate.

FIG. 20 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate. Another manufacturing technique that would allowthe use of a fully non-conductive substrate is shown in FIG. 20. A smallarea of each LED diode would be etched down to a layer below the P-Njunction to allow a bonding wire to be attached, allowing the electricalchaining of the LED diodes to be completed from the front side of theoriginal wafer only.

FIG. 21 illustrates an LED light string constructed according to yetanother embodiment of the present invention in a multiple layer semiconductive substrate. In FIG. 21 narrow channels are etched into thewafer on both sides to eliminate P-N junctions that are not desired.Combining this technique with conductive wires attached on both sides ofthe wafer, we can again create a string of LED diodes from a singlepiece of silicon.

While FIG. 21 shows a side view of such a device, a 2 dimensional matrixof LED devices may be formed on the surface of a wafer, allowing LEDdiodes to be created with simultaneous large surface area for largelight output levels divided into a large number of LED diodes connectedin a series string, as shown in FIG. 22, which illustrates an LED lightstring constructed according to yet another embodiment of the presentinvention in a multiple layer semi conductive substrate.

The terms “circuit” and “circuitry” as used herein may refer to anindependent circuit or to a portion of a multifunctional circuit thatperforms multiple underlying functions. For example, depending on theembodiment, processing circuitry may be implemented as a single chipprocessor or as a plurality of processing chips. Likewise, a firstcircuit and a second circuit may be combined in one embodiment into asingle circuit or, in another embodiment, operate independently perhapsin separate chips. The term “chip,” as used herein, refers to anintegrated circuit. Circuits and circuitry may comprise general orspecific purpose hardware, or may comprise such hardware and associatedsoftware such as firmware or object code.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention. One of average skill in the art will also recognize that thefunctional building blocks, and other illustrative blocks, modules andcomponents herein, can be implemented as illustrated or by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or any combination thereof.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “coupled to” and/or “coupling” and/or includes direct couplingbetween items and/or indirect coupling between items via an interveningitem (e.g., an item includes, but is not limited to, a component, anelement, a circuit, and/or a module) where, for indirect coupling, theintervening item does not modify the information of a signal but mayadjust its current level, voltage level, and/or power level. As mayfurther be used herein, inferred coupling (i.e., where one element iscoupled to another element by inference) includes direct and indirectcoupling between two items in the same manner as “coupled to.” As mayeven further be used herein, the term “operable to” indicates that anitem includes one or more of power connections, input(s), output(s),etc., to perform one or more its corresponding functions and may furtherinclude inferred coupling to one or more other items. As may stillfurther be used herein, the term “associated with,” includes directand/or indirect coupling of separate items and/or one item beingembedded within another item. As may be used herein, the term “comparesfavorably,” indicates that a comparison between two or more items,signals, etc., provides a desired relationship. For example, when thedesired relationship is that signal 1 has a greater magnitude thansignal 2, a favorable comparison may be achieved when the magnitude ofsignal 1 is greater than that of signal 2 or when the magnitude ofsignal 2 is less than that of signal 1.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the invention.

Moreover, although described in detail for purposes of clarity andunderstanding by way of the aforementioned embodiments, the presentinvention is not limited to such embodiments. It will be obvious to oneof average skill in the art that various changes and modifications maybe practiced within the spirit and scope of the invention.

1. A Light Emitting Diode (LED) light apparatus comprising: a bridgerectifier configured to be powered by an alternating current powersource and to produce a rectified output; control circuitry coupled tothe bridge rectifier, the control circuitry configured to produce ashunt signal when the rectified output is less than a threshold voltage;a series connected Light Emitting Diode (LED) string comprising a firstgroup of LEDs and a second group of LEDs; and a switch coupled to afirst side of the second group of LEDs and controlled by the shuntsignal to deactivate the second group of LEDs.
 2. The LED lightapparatus of claim 1, wherein a number of the first group of LEDs isapproximately equal to a number of the second group of LEDs.
 3. The LEDlight apparatus of claim 1, wherein each of the first group of LEDs andthe second group of LEDs includes at least one LED.
 4. The LED lightapparatus of claim 1 wherein the control circuitry comprises: a ratiometric series resistor string configured to sense a proportion of therectified output; and an inverter configured to generate the shuntsignal based on the proportion of the rectified output.
 5. The LED lightapparatus of claim 4, wherein the inverter comprises: a transistorconfigured to receive the proportion of the rectified output; and aresistor coupled to the transistor and configured to generate the shuntsignal based on the proportion of the rectified output.
 6. The LED lightapparatus of claim 4, wherein the switch comprises a field effecttransistor having: a gate configured to receive the shunt signal; and adrain and source connected in shunt across the second group of LEDs. 7.The LED light apparatus of claim 4, wherein the switch comprises abipolar transistor having: a base configured to receive the shuntsignal; and an emitter and collector connected in shunt across thesecond group of LEDs.
 8. A Light Emitting Diode (LED) light apparatuscomprising: a bridge rectifier configured to be powered by analternating current power source and to produce a rectified output;control circuitry coupled to the bridge rectifier, the control circuitryconfigured to produce a first shunt signal based upon the rectifiedoutput and at least one first voltage threshold and to produce a secondshunt signal based upon the rectified output and at least one secondvoltage threshold; a series connected Light Emitting Diode (LED) stringcomprising a first group of LEDs, a second group of LEDs, and a thirdgroup of LEDs; a first switch coupled to a first side of the secondgroup of LEDs and controlled by the first shunt signal to deactivate thesecond group of LEDs; and a second switch coupled to a first side of thethird group of LEDs and controlled by the second shunt signal todeactivate the third group of LEDs.
 9. The LED light apparatus of claim8, wherein a number of the second group of LEDs is approximately equalto a number of the third group of LEDs.
 10. The LED light apparatus ofclaim 8, wherein each of the first group of LEDs, the second group ofLEDs includes at least one LED, and the third group of LEDs includes atleast one LED.
 11. The LED light apparatus of claim 8, wherein thecontrol circuitry comprises: a ratio metric series resistor stringconfigured to sense a first proportion and a second proportion of therectified output; a first inverter configured to generate the firstshunt signal based on the first proportion of the rectified output; anda second inverter configured to generate the second shunt signal basedon the second proportion of the rectified output.
 12. The LED lightapparatus of claim 11, wherein: the first inverter comprises a firsttransistor configured to receive the first proportion of the rectifiedoutput and a first resistor coupled to the transistor and configured togenerate the first shunt signal based on the first proportion of therectified output; and the second inverter comprises a second transistorconfigured to receive the second proportion of the rectified output anda second resistor coupled to the second transistor and configured togenerate the second shunt signal based on the second proportion of therectified output
 13. The LED light apparatus of claim 12, wherein thefirst switch comprises a field effect transistor having: a gateconfigured to receive the first shunt signal; and a drain and sourceconnected in shunt across the second group of LEDs.
 14. The LED lightapparatus of claim 12, wherein the first switch comprises a bipolartransistor having: a base configured to receive the first shunt signal;and an emitter and collector connected in shunt across the second groupof LEDs.
 15. A method for operating a Light Emitting Diode (LED) lightcomprising: rectifying an alternating current power source and toproduce a rectified output; producing a shunt signal when the rectifiedoutput is less than a threshold voltage; and for a series connectedLight Emitting Diode (LED) string comprising a first group of LEDs and asecond group of LEDs, closing a switch coupled to a first side of thesecond group of LEDs by the shunt signal to deactivate the second groupof LEDs.
 16. The method of claim 15, wherein a number of the first groupof LEDs is approximately equal to a number of the second group of LEDs.17. The method of claim 15, wherein a number of the first group of LEDsis greater than a number of the second group of LEDs.
 18. The method ofclaim 15, wherein producing a shunt signal when the rectified output isless than a threshold voltage comprises: sensing a proportion of therectified output across a ratio metric series resistor string; andgenerating the shunt signal based on the proportion of the rectifiedoutput.
 19. The method of claim 15, wherein closing the switch comprisesturning on a field effect transistor having a drain and source connectedin shunt across the second group of LEDs.
 20. The method of claim 15,wherein closing the switch comprises turning on a bipolar transistor anemitter and collector connected in shunt across the second group ofLEDs.